It has previously been shown that both cranial and trunk neural crest cells can give rise to several different cell types. However, only the cranial neural crest cells are capable of differentiation into craniofacial mesenchyme to give rise to bone, muscle and connective tissues. Our hypothesis is that selective gene expression in the early cranial crest allows cranial mesenchymal differentiation To test this hypothesis, we have generated cDNA of chick cranial and trunk neural cell outgrowths from neural tube explants for differential mRNA display screening to identify cranial crest specific genes. We have been able to tentatively identify several cDNAs that are differentially expressed in the cranial crest cells. At this time we are continuing to characterize these genes via in situ hybridization utilizing the cloned cranial crest specific cDNAs. Corroborating evidence is provided by slot blot analysis. All of the evidence accrued thus far points to a genetic event, as yet, not well characterized, which is confined to the cranial neural crest.